1. Field of the Invention
The present invention generally relates to methods of setting up a backup path, and particularly relates to a method of setting up a backup path prior to the occurrence of a failure on a network as protection against a failure of a primary path.
2. Description of the Related Art
FastReroute is a method for failure recovery used in an MPLS (Multiprotocol Label Switching) network. In this method, a request for setting up a primary path including a request for setting up a backup path is issued from a head-end node of a primary path to a tail-end node, thereby setting up the primary path and also simultaneously setting up a backup path at each node other than the tail-end node on the primary path so as to bypass an adjacent node or link situated downstream. This makes it possible to provide protection against any node failure and link failure that may possibly occur on the primary path, and to set up backup paths prior to the occurrence of failure, thereby achieving high-speed switching of paths at the time of failure.
Patent Document 1 (Japanese Patent Application Publication No. 2000-324167) discloses selecting a bypass route between the two nodes that sandwiches a point of failure at the time of failure among a particular set of nodes selected beforehand on the path. Patent Document 2 (Japanese Patent Application Publication No. 2003-32289) discloses reducing link resources that are consumed by backup communication connections provided as the protection of main communication connections in a connection-oriented network. Patent Document 3 (Japanese Patent Application Publication No. 2001-186178) discloses a packet that is transmitted from a transmission end, and, upon failure to arrive at a receiver terminal, returns to a router based on header information and setting information after other header information is attached thereto. This packet is then transmitted to a backup path so as to arrive at the receiver terminal after the added header information is removed at the router.
In a method for failure recovery such as FastReroute, backup paths are provided at every node except for the tail-end node on a primary path. In FIG. 1, a primary path is provided, with a node 1 serving as a head-end node and a node 4 serving as a tail-end node, thereby connecting between nodes 1, 2, 3, and 4. In this case, a path connecting between nodes 1, 5, and 2, a path connecting between nodes 2, 6, and 3, and a path connecting between nodes 3, 7, and 4 are provided as backup paths for bypassing links. Further, a path connecting between nodes 1, 8, and 3 and a path connecting between nodes 2, 9, and 4 are provided as backup paths for bypassing the nodes 2 and 3, respectively.
In this manner, a large number of backup paths are provided. When such a method for failure recovery is employed, network providers must face a problem of excess consumption of network resources such as frequency bands since a large number of backup paths having no traffic during a normal operation are set up. Further, there is a problem of an increase in unwanted traffic as control messages for a large number of backup paths are transmitted through the network for the purpose of checking the validity of backup path routes even after the setting up of the backup paths.
Accordingly, there is a need for a method and apparatus for setting up backup paths that can reduce the number of backup paths to avoid excess consumption of network resources and prevent an unwanted increase in traffic.